An autonomous vehicle, also known as a driverless or robot car, is an automated vehicle in which there is no human driver. In an autonomous vehicle that is transporting human passengers, without a human driver able to bring the moving vehicle to a halt, a potentially failing subsystem such as, e.g., power brakes, power steering, robotic steering controller, robotic braking controller, robotic accelerator controller etc., is a risk that must be mitigated. One possible reason for a subsystem failure is loss, or deterioration, of automotive-battery electrical power in a hybrid autonomous vehicle, where such power would otherwise normally be properly supplied to that subsystem.